The present invention relates to printers which are used to print information on price tags or labels, and more particularly to a support structure which is able to maintain a thermal print head within the printer so that the print head will apply an optimum and uniform printing pressure to labels, in a manner which is insensitive to the width of the labels or to variations in the nature of the contact which develops between the labels and the thermal print head as the labels are being fed.
FIG. 10 shows a typical price tag strip 1. It consists of a strip of backing sheet 2 coated on its front surface with a separating agent and a plurality of labels 3 detachably adhered continuously along the length of the backing sheet 2. The labels 3 are coated with a pressure-sensitive adhesive However, some labels or tags do not use pressure-sensitive adhesive. Positioning marks 4 appear on the rear surface of the backing sheet 2. In the familiar manner, the labels 3 are printed with data related to the products on which they are usually used and these labels are then adhered to those products, forming price tags or any other identifying tags.
Price tags or labels come in long, rolled up strips. A roll of labels is loaded into a printer and the labels are imprinted with appropriate information and are either paid out singly through the front of the label printer or rolled up onto a take-up roller to provide an operator with a roll of imprinted labels or price tags. At a thermal printing section in the printer, where the labels pass between a platen and a thermal print head, slight variations occur in the nature of the contact which develops between the thermal print head and the labels. The nature of the contact is dependent on the manner in which the labels are fed. In any case, the variations in contact induce undesirable variations in the printing pressure being applied to the labels by the thermal print head. The problem is present regardless of whether single or strips of labels are fed through the printer.
Labels/price tags come in different widths and the width of labels also affects how the print head contacts the labels. This further complicates the ability to maintain optimum printing pressure across labels, and therefore the printing quality.
Another problem arises from the difficulty of assembling the thermal print head and the platen of a printer so that they extend perfectly parallel to one another. This too leads to the application of an uneven pressure across the labels and therefore to uneven printing. The aforementioned problems affect both labels and price tags.